Question

请教SAT语法，谢谢！

The Pony Express was an ingenious system for carrying "mail; it was in existence only briefly, however," before the telegraph system made it obsolete.

引号部分为画线部分
A.mail; it was in existence only briefly, however,
D.mail, having existed only briefly

答案说这道题选A，请问A中的it是指"The Pony Express"吗？

为什么D答案不对呢，在SAT语法中，有一条规则：subject+verb+object, doing(逗号后面的doing修饰主语subject) 所以我认为D中的having existed...修饰“The Pony Express"，不对吗？

Answer 1

这个句子是由分号分隔的两个并列句。

第二分句 it was in existence only briefly, however," before the telegraph system made it obsolete 中，the telegraph system made it obsolete 的代词 it 显然是指代 Pony Express，也就是说是由于 telegraph system（电报系统）的出现才使得 Pony Express不再使用，因此 in existence only briefly（存在时间很短暂）当然也应该指代 Pony Express。

而在名词后用逗号分隔的分词短语相当于一个非限制性定语从句，其作用是就近对该名词给予补充说明，因此 having existed 是用来说明 mail 的，而不是 Pony Express，（等于 the mail had existed only briefly before …）。这样，句子的意思就变成了“在电报系统使得传递邮件不再使用以前，邮件只存在了很短暂的一段时间”，这显然是不符合事实的。

因此，答案 D 不对站不住脚，不能成立。

追问

thank you, but how do you explain this: "subject+verb+object, doing, 逗号后面的doing修饰主语subject, 不对吗？

追答

In the prase "subject + verb + object, doing...", the -ing form is a present participle and is used to additional remark the object; therefore, its logic subject is the object of the sentence rather than the subject. If such a form is used to modify the subject, the phrase must be changed into "subject, doing... + verb + object, "
It seems that I have explained it clearly in my Chinese explanation above: 而在名词后用逗号分隔的分词短语相当于一个非限制性定语从句，其作用是就近对该名词给予补充说明，因此 having existed 是用来说明 mail 的，而不是 Pony Express，（等于 the mail had existed only briefly before …）。这样，句子的意思就变成了“在电报系统使得传递邮件不再使用以前，邮件只存在了很短暂的一段时间”，这显然是不符合事实的。

追问

but in SAT grammer, " S+V+O doing" , if there is no comma behind the object, then "doing" will motify object, but if there is a comma behind object, the "doing" will motify object, that's the difference between" S+V+O doing" and "S+V+O, doing", do you know much about SAT grammer?

Thank you!

追答

In " S+V+O doing" , there is no comma, while in "S+V+O, doing" the comma is after the O. So, it is the comma that makes a difference from each other.
As for SAT grammer, I think it is also English garammer, and only its pertinency has some particularity in a way.

追问

so for my question above, according to SAT grammer, if there is a comma behind object, the "doing" will motify object, and thus "having existed..." should motify "The Pony Express", why D is not right?

Answer 2

嗯，我认同张达人zhdr对A选项的解释。但是对于D选项。从时态方面，就可以看出不合理之处。having existed用于过去式似乎有些牵强。